Method for production of metal
fabrications



United States Patent 26,042 METHOD FOR PRODUCTION OF METAL FABRICATIONSJohn J. Grebe and John F. Miller, Midland, Micl1., as-

signors to The Dow Chemical Company, Midland, Mich., a corporation ofDelaware N0 Drawing. Original No. 3,201,228, dated Aug. 17, 1965, Ser.No. 216,296, Aug. 13, 1962. Application for reissue Sept. 30, 1965, Ser.No. 492,366

7 Claims. (Cl. 75-33) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification;rna-tter printed in italics indicates the additions made by reissue.

This application is a continuation-impart of application Serial No,113,657, filed May 31, 1961, now abandoned, which in turn is acontinuation-in-part of application Serial No. 823,155, filed June 26,1959, now Patent No. 2,990,267.

This invention is concerned with an improved method for preparing formedmetal products. It more particularly relates to a method for theproduction of metal and alloy products from metals having co-producedtherewith an alkali metal silicate, glass-like protective slag.

The method of the present invention has as its principal object thepreparation of metal products by hot working sponge or particulatemetals formed by low temperature reduction of metal ore or metal oxidesin the presence of a co-produced alkali metal silicate glass-like slag.

A further object of the present invention is to provide high-grade metalfabrications starting from low quality readily available oxidized metalvalue containing materials.

Another object of the present invention is to provide metal fabricationswhich are produced directly from the reaction products resulting fromthe reduction of ores or other materials containing oxidized forms ofmetals which are reducible by the method of the instant process.

It is still another object of the present invention to provide a methodfor preparing alkali metal silicate glass-like slag along with a reducedmetallic product which slag can be reclaimed and economically convertedinto useful, commercially important products.

It is also an object of the present invention to provide a metalreduction process whereby there is substantially complete elimination ofundesirable contaminating gases from the metal product because ofcoproduction of the alkali metal silicate glass slag which envelopes themetallic product as produced thereby preventing atmosphericcontamination.

An additional object of the present invention is to provide a method forproducing fabricated metal products wherein a protective glass-likecoating is formed and bonded to the outer metal surface or throughoutthe fabrication during the forming operation.

It is another object of the present invention to introduce alkali metaloxide scavengers into a metal producing composition without encounteringundesirably high losses from volatilization.

It is still a further object of the present invention to provide aneconomical metal winning process where extra heat is obtained fromexothermic reactions during the reduction process.

These and other objects and advantages will be recognized by one skilledin the art from the detailed description of the invention presentedhereinafter.

The combination of steps as practiced in the method of this inventioncomprises, in general, mixing a comminuted metal ore or materialcontaining reducible metal values and a silicate slag fluxing agent withfinely divided carbonaceous material or other reducing agent and analkali metal oxide or oxide former, i.e., alkali metal hy- Re. 26,042Reissued June 14, 1966 droxide, for example. Sufficient molarproportions of the ore and reducing agent are used to insuresubstantially complete reduction of the metal to the metallic state andsulficient quantities of alkali metal oxide or oxide former and silicatefiuxing agent are employed to insure formation of a continuous, fusedglass-like slag. This mixture is heated at temperatures within the rangeof from about 450 centigrade to about 1225 centigrade for a timesufficient to achieve simultaneous reduction of the metal values in theore and production of the alkali metal silicate glasslike slag. Duringthis period, the reduction is aided by exothermic reactions involvingthe alkali metal values. The resulting hot product mass, comprised ofdiscrete solid substantially gas-free metallic particles or sponge metalencased in a plastic glass-like slag is then hot worked.

The term hot working as used herein is meant to include both mechanicalWorking and molten melting forming operations such as melting, castingand the like.

The mechanical hot working or forming operations can be carried out byany of a number of hot working processes including, for example, hammerforging, hot rolling, hydraulic press forging, mechanical press forging,upsetting, extruding, roll forging, die rolling, hot deep drawing,swaging, rotary swaging and the like. In this process the metaltreatment is carried out at a temperature at which the glass remainsmolten thereby compacting and forming the metal while in the presence ofthe protective glass-like slag. For some fabrication several of theabovementioned processes can be used in combination to produce thedesired product form. The instant process which is suitable forfabricating a wide variety of metals finds particular utility in thepreparation of iron based fabrications.

The type and amount of mechanical hot working to be carried out on thehot product mass will vary depending on the desired form of the metalproduct and the characteristics and properties of the metal itself. Toillustrate, a small amount of working, for example hammer forging, canproduce, from sponge iron produced by the reduction process of theinstant invention, a core wherein the iron network is surrounded by aninert glass-like slag coating which upon cooling hardens into aprotective substantially pore free coating. Continued or extendedforging of the hot metal sponge-plastic glass-like slag coproducts forlonger periods produces a silicate glass fiber-reinforced compacted ironcore for example. Still further kneading, folding, hammering andsqueezing of the product mixture by the forging operation leads to adense compact iron core and extruding of the molten glass-likeco-product to the outside of the formed mass. These latter two mentionedproducts readily lend themselves to extrusion practices as the glasscoating and/or fibers contained therein serve as an excellent dielubricant.

The metal sponge product encased in its protective glass-slag also canbe introduced into conventional melting furnaces and taken into themolten state whereupon the metal can be cast into ingot form or otherpredetermined shapes or otherwise utilized in molten metal formingoperations. For such operations, ordinarily the bulk of the protectivealkali metal silicate glass from the low temperature forming operationis removed prior to the melting operation. Conveniently, this is merelypoured off as this slag usually is molten or can be made molten at metalsponge forming temperatures. Only a relatively small amount of the slagwhich encases the sponge as produced is necessary to provide a goodprotective cover for the charge during the subsequent melting operation.

Although the sponge, a solid particulate metal product mass, as producedcan be employed directly for subsequent melt operation, also it is to beunderstood that because of its protective alkali silicate glass coatingit can readily be stored, shipped or otherwise handled prior to its usein melting and coating operations.

The initial sponge or particulate metal product mass also lends itselfreadily to other hot working operations. For example, a metal billetwhich has been forged or swaged to an extent that some glass fibersremain in the billet readily can be extruded. The glass-like slag fiberinclusions act as a die lubricant during the forming operation, and, inthe extruded product serve to add to the strength and corrosionresistance of the formed product. Also, extrusion of a forged or upsetingot, wherein substantially all of the slag has been forced to theoutside and remains there as a surface coating, leads to production ofglass coated pipe, conduit and other structural members. Such members,the surfaces of which are substan tially inert to a wide variety ofcorrosive atmospheres and environments, can find use in a wide varietyof applications which have need for light weight and long livedstructural elements.

Hot rolling of the product mass can produce a metal sheet havingessentially a porcelain-type coating integrally produced during therolling operation.

In any of the above-mentioned applications wherein the glass-likeprotective coating is produced on the metal surface, such coating can begiven a decorative effect by incorporating pigments, such as are used inglazing and porcelainizing operations, into the mass prior to the hotworking.

Although the instant process is particularly adaptable to the productionof surface protected fabrications, as has been set forth hereinbefore,the metal can be worked to remove substantially all of the slagtherefrom. In the continued mechanical working of the product mass, theglass-like slag product becomes heated to successively highertemperatures thereby becoming less viscous and less dense. It is readilysqueezed to the surface of the metal compact and finally issubstantially removed from within the metal compact. In this operation,the continuous exudation of the glass from the compact, during the hotworking, serves to protect the metal from oxidation. In meltingoperations the less dense molten protective glass is poured or otherwiseseparated from the molten charge before coating, e.g. in accordance withstandard foundry and molten metal handling techniques.

In carrying out the low temperature metal reduction stage of the processof the instant invention many of the metal ores, as mined, or metalcontaining materials advantageously will contain varying amounts ofsilica or other siliceous material such as complex silicates and thelike. However, in many cases these silicon containing,

glass forming, fluxing materials are not present or are present inextremely small amounts. If these are not present in sufficientquantities for production of the glasslike slag, excess silicon dioxidein the form of sand or powdered quartz can be added to the mix.Production of the slag itself results from reaction of silicon dioxideand/or other silicate glass forming fluxing agents present with thealkali metal oxide former used in the mix. Potassium-sodium-and lithiumhydroxide or the corresponding carbonates all have been found to besuitable for this application although sodium hydroxide is preferred.The alkali metal hydroxide, which can contain the impurities found incommercial grades of the product, is used in any of a number of formsincluding substantially dry flake, paste or as an aqueous solution.

The reducing agent normally used in the process is carbon or a materialhaving a high free carbon content. Soft coal and lignite, both of whichare plentiful and inexpensive, have been found to work verysatisfactorily as reducing agents in the method of the invention.However, other reductants which can be employed include metals such assodium, calcium, potassium, lithium, magnesium and silicon,carbon-containing compounds, certain metal salts or hydrides and thelike.

The reaction temperatures to be employed in the preparation of thereduced metal containing product mass can range from about 450centigrade to about 1225 centigrade and reaction time can vary fromabout 1 to about 180 minutes and more, this time depending both on thereaction temperature employed and metal being produced. In any event thereaction will be carried out at a temperature at which the metal remainsin a solid but plastically deformable form during the reduction step.

The time of reaction to achieve metal reduction will vary in an inversemanner to the temperature employed. For example, iron oxide can bereduced to metallic iron by reaction at about 1225 Centigrade for about25 minutes while a reaction time of about 180 minutes is required attemperatures of about 900 centrigradc. For the different metals, it willbe recognized that both reaction times and temperatures are dependent onthe properties of these individual metals. The elements whose standardelectrode potentials approach more closely those of the noble metals canbe reduced with considerably greater easelower temperatures and reactiontimes than those elements near the upper temperature limits ofapplication of the invention, namely manganese, chromium and the like.

It readily is understood that the process is suitable for use not onlyin the production of a given metallic element, but by a predeterminedselection of metal oxides that solid metal alloys are produced directlyin the low temperature reduction step.

Illustrative of an embodiment of this invention is a method for theproduction of finely divided or sponge iron encased in a glass-like slagand the subsequent hot working of the metal-slag mass by hammer forging.For this process, the reaction mixture was prepared by mixing acomminuted iron containing ore (selected from ores ranging in ironcontent from that of the high quality hermatics [60-65% iron] to thelowest grade taconites [15-25% iron]) either in the presence or absenceof excess silica. that is silica in excess of that provided by thegangue material, with a finely divided carbonaceous material and analkali metal hydroxide. The preferred operating compositions of thereaction mixture preferably fall within the range of 0.05 to 3.0 molesof silicon dioxide, 1.0 to 3.0 moles of carbonaceous material and 0.3 to4.0 moles of the alkali metal hydroxide per mole of the iron oxidecontent of the ore although effective conversion of the ores intometallic iron can be obtained even though the reaction is run usingcompositions outside this range.

The reaction components described above were mixed thoroughly in aconventional mixer, then placed preferably in a melting pot or crucibleand transferred to a furnace. This furnace conveniently can be eitherelectrically heated and supplied with a protective atmosphere such asnitrogen, helium, argon or even the carbon monoxide itself present inthe reacting system. Alternatively, the furnace can be gas fired. In thelatter case, excess fuel gas along with the combustion product gasesprovide the mixture with a natural protective atmosphere. As analternate to this bath type operation, the mix can be fed from the mixerat a continuous, controlled rate onto a moving grate so timed as to givethe desired reduction and dispersion of the metallic particles in asingle pass through the furnace. The reaction mixture was heated withinthe range of about 900 to about 1225 C for a period from about 30 toabout 180 minutes, and, preferably at about 1100 centigrade for about 30to 40 minutes. The resulting soft, sponge iron and glass-like slagproduct then was subjected to kneading, folding and squeezing by thepounding action of the forging process. As this forging operationproceeds, the low melting slag was forced to the outside of the mass anda dense, compact substantially solid iron core resulted. Ordinarily, noadditional external heat need be supplied during the forking operationas the friction and kinetic energy supplied during the hot workingitself may be sufficient to keep the slag fluid and the iron in aworkable state. Such hot working also can give desirable randomdistribution of the stress forces in the resulting fabrication.

The following examples will serve to further illustrate the presentinvention.

EXAMPLE 1 Ground taconite ore, 951.9 grams (containing approximately 3moles Fe O based on 50 percent Fe O in ore, and approximately 6 molesSiOz. based on 39 percent Si0 in ore), 107.8 grams (equivalent toapproximately 9 moles of carbon) of ground soft coal and 494 grams(approximately 12 moles) of flake sodium hydroxide were thoroughly mixedand placed in a clay graphite crucible. The crucible and contents wereplaced in gas fired furnace and held at about 1210 C. for about 35minutes. After this time, the crucible was removed from the furnace anda portion of the lower density glass-like slag was poured from the topof the crucible. The remainder of the sponge iron-plastic slag mixturewas removed from the crucible as an integral mass.

The hot mass was worked by hammering following a general procedure asemployed in the hammer forging operations. The working of the mass wascontinued until the metal sponge was compacted into a densesubstantially solid core. During this operation, the slag, originallyentrapped within and surrounding the metal sponge, was squeezed to theoutside of the resulting iron billet.

In a second run utilizing the same mix and reaction conditions, the ironsponge-plastic slag produced was hammer-forged in the same manner asdescribed heretofore but the action was discontinued before the densesubstantially solid core of metal was produced. The billet was cut intosections. Examination of the exposed cross-section indicated the billetwas composed of a network of glass-like fibers tenaciously bonded to thepartially compacted metal.

In a third run utilizing the same mix and reaction con- I ditions, theiron sponge with its coating of protective alkali metal silicate glasswas placed in a crucible and melted. The molten iron was cast into amold using standard foundry techniques. Examination of the cast productshowed substantially no slag inclusions or voids therein.

EXAMPLE 2 A mixture of iron ore, carbon and caustic was prepared as setforth in Example 1. After mixing, about percent water, based on thetotal weight of the mixture, was blended into the batch and thisresulting moist mix extruded into a ribbon about 0.5 inch wide and about0.25 inch thick. A length of ribbon was placed in a graphite boat andthis introduced into a preheated electric furnace maintained at about1220" C. The mix was heated for about 30 minutes. After this time theheated ribbon was removed from the furnace and while hot was hammerforged and swaged into a predetermined compacted shape. Examination ofthe product after compaction indicated the fabrication was substantiallyof solid metal having a few fibers of glass dispersed throughout thestructure. EXAMPLE 3 Ground nickel oxide (NiO), 500 grams, about 25grams of SiO about 33.3 grams of flake sodium hydroxide and about 23.5grams of ground soft coal were thoroughly mixed and placed in a claygraphite (Plumbago) crucible. This mix gave a Na O/SiO equivalent grammolar ratio of 1 and a NiO/C gram molar ratio of 1.

The crucible and contents were placed in a gas-fired furnace at about400 C. The furnace was then heated to a temperature of about 1220 C.over a period of about 35 minutes and maintained above 1200 C. for about40 minutes additionally. Following the reaction period, the crucible wasremoved from the furnace and the bulk of the less dense alkali metalsilicate poured off. The metal sponge encased in a protective coating ofthe glass, which served to substantially eliminate the formation ofundesirable gas inclusions in the metal product, was transferred to asecond crucible and placed in an electric resistance furnace. Thefurnace was heated and the nickel transformed into the molten state. Themetal first collected as small beads. These coalesced into larger beadsand then into a solid mass. The residual glass coating, being less denseremained in a molten layer on top of the metal during the meltingserving as a protective layer. The molten metal then was transferredinto a mold and cooled.

EXAMPLE 4 Using the same techniques and procedures as described forExample 3, metallic cobalt was prepared from a charge consisting ofabout 500 grams ground C00, about 17.6 grams SiO about 23.4 grams flakesodium hydroxide and about 56.4 grams powdered soft coal.

EXAMPLE 5 Using the same techniques and procedures as described forExample 3, metallic manganese was prepared from a charge consisting ofabout 500 grams manganese bearing ore (SiO present in the native ore4.5%), about 30 grams flake sodium hydroxide and about 29.6 gramspowdered soft coal.

EXAMPLE 6 A mixture of about 2 parts by weight nickel oxide, 1 part byweight copper oxide along with small amounts of iron oxide and manganeseoxide can be mixed and these reacted with the requisite amounts of Slog,Na O values and carbon to produce directly a Ni-Cu based alloy byfollowing the procedures of the present process.

In a manner similar to that shown in the foregoing examples, and usingthe corresponding metal ore, silica, carbonaceous material and alkalihydroxide, zinc can be obtained from its ore by heating for a sufiicientperiod at a temperature of about 1225 centigrade. Similarly, lead can beproduced at a temperature about 450 centigrade.

Although these examples have merely shown preferred embodiments of thisinvention, it is also understood that other oxidized metal compounds canbe utilized in this process to produce a wide variety of formed metalswhose standard electrode potentials range from about 1.2 to about minus0.85, including tellurium, zinc, chromium, gadolinium, cadmium, indium,thallium, cobalt, nickel, tin, antimony, bismuth, arsenic, copper,silver and the like. Furthermore, by using mixtures of the oxidizedmetal compounds, alloys also can be produced directly.

Various modifications can be made in the method of the present inventionwithout departing from the spirit or scope thereof and it is understoodthat we limit ourselves only as defined in the appended claims.

We claim:

1. An improved method for the production of metal products of thosemetallic elements having a standard electrode potential falling betweenabout 1.2 and about minus 0.85, which comprises: contacting an oxidizedform of said metal selected from the group consisting of comminutedmetal ores and materials containing reducible metal values and silicateglass forming fluxing agent with a member selected from the groupconsisting of [an] alkali metal [hydroxide] oxides or oxide formers, anda solid carbonaceous reducing agent at temperatures from about 450 toabout 1225 centigrade for a period of time sufficient to yield the solidmetal substantialy free from undesirable gaseous inclusions suspended ina continuous, fused alkali metal silicate glass-like thermoplastic slag,separating the major portion of the less dense slag, while in the moltenstate, from the solid metal product, heating said solid metal productinto the molten state whereby the metal is compacted into a continuousmass and the remainder of the protective alkali metal silicateglass-like slag enveloping said mass rises to the surface of the meltthereby providing a protective cover for the substantially gas-freemetal during the melting operation, and casting said molten metal.

2. The process as defined in claim 1 wherein the metal product is analloy prepared directly by providing a mixture of oxidized metals havinga standard electrode potential falling between about 1.2 and about minus0.85 as a reactant in the initial solid metal reduction step of saidprocess.

3. A method for producing nickel products which comprises: contacting anickel oxide containing material with a member selected from the groupconsisting of [an] alkali metal [hydroxide] oxides r oxide formers, asili cate glass forming fluxing agent and a solid carbonaceous reducingagent at a temperature of about 1200 C. for about 40 minutes thereby toproduce directly solid sponge nickel in a protective alkali metalsilicate glass, separating a portion of the glass while in the moltenstate from the nickel sponge, transferring the nickel sponge to amelting furnace, melting said nickel sponge and casting said nickelmelt.

4. A method for producing cobalt products which comprises: contacting acobalt oxide containing material with a member selected from the groupconsisting of [an] alkali metal [hydroxide] oxides or oxide formers, asilicate glass forming fluxing agent and a solid carbonaceous reducingagent at a temperature of about 1200 C. for about 40 minutes thereby toproduce directly solid cobalt in a protective alkali metal silicateglass, separating a portion of the glass while in the molten state fromthe cobalt. transferring the cobalt to a melting furnace, melting saidcobalt and casting said cobalt melt.

5. A method for producing manganese products which comprises: contactinga manganese oxide containing material with a member selected from thegroup consisting of [an] alkali metal [hydroxide] oxides 0r oxideformers, a silicate glass forming fluxing agent and a solid carbonaceousreducing agent at a temperature of about 1200 C. for about 40 minutesthereby to produce directly solid manganese in a protective alkali metalsilicate glass, separating a portion of the glass while in the moltenstate from the manganese, transferring the manganese to a meltingfurnace, melting said manganese and casting said manganese melt.

6. An improved method for the production of hot Worked iron fabricationswhich comprises: contacting a reducible iron compound with a memberselected from the group consisting of [an] alkali metal [hydroxide]oxides or oxide formers, a silicate glass forming fluxing agent and asolid carbonaceous reducing agent at temperatures from about 900 toabout 1225 centigrade for about 30 to about 180 minutes to yield anetwork of solid iron suspended in alkali metal silicate glass-likeslag, mechanically hot working the so-produccd hot product mass in thepresence of said glass-like protective slag thereby compacting said ironinto a fabrication of predetermined shape and continuing the hot workingof the product mass until substantially all of the glass-like slag hasbeen removed from the interior of the compacted fabrication.

7. An improved method for the production of fabricated iron productswhich comprises: contacting an iron ore with sufiicient silica to makethe content at least 0.05 mole, per mole of iron oxide present,sufficient solid carbonaceous material to make the content at least 1.0mole per mole of iron oxide present and sutficient amounts of a memberselected from the group consisting of an alkali metal [hydroxide] oxidesor oxide formers to make the content at least 0.3 mole per mole of ironoxide present, heating the mixture at about 900 to about 1225 Centigradefor about 30 to about 180 minutes in an inert atmosphere, Working theresulting dispersion solid iron particles in the presence of coproducedalkali metal silicate fluid, viscous slag thereby compacting said ironand exuding the slag to the exterior of the so-worked compact.

References Cited by the Examiner The following references, cited by theExaminer, are of record in the patented file of this patent or theoriginal patent.

UNITED STATES PATENTS 2,684,296 7/1954 Moklebust -33 2,728,655 12/1955Brudin 75-33 2,757,078 7/1956 Edstrom 7533 2,767,087 10/1956 Cavanagh75-33 2,839,397 6/1958 Cavanagh 7533 2,880,083 3/1959 Weinert 75332,990,267 6/1961 Grebe et al 7530 DAVID L. RECK, Primary Examiner.

H. W. TARRING, Assistant Examiner.

